1. Technical Field
The present invention generally relates to illumination devices for illuminating non-emissive displays, such as LCD displays, floor mats, and large-size logo display boards and, particularly to an illumination device uniformly guides input light onto its top surface thereof.
2. Description of Related Art
Non-emissive display devices such as LCD panels, floor mats, or logo display boards are commonly used in daily life. External light sources are applied in the display devices for providing illuminations for the non-emissive display devices. LED (light emitting diode) is preferably used in the non-emissive display devices instead of CCFLs (cold cathode fluorescent lamp) due to its brightness, long life-span, and wide color gamut. This is disclosed in IEEE Transactions on Power Electronics, Vol. 22, No. 3, entitled “Sequential Color LED Backlight Driving System for LCD Panels”, and published by Chen et al. in May 2007, the disclosure of which is incorporated herein by reference.
A typical illumination device includes a light guide block and an array of point light sources. Lights emitted from the point light sources are converted into a surface light and provide illuminations for the non-emissive display devices. However, a radiation angle of each of the point light sources is usually less than 120°, which induces a peripheral portion of the display devices to be darker than a central portion thereof. This causes the light to non-uniformly distribute over the display devices. Therefore, there is a need for improving the display efficiency of the display devices.